Although Prime Minister Narendra Modi has vowed to protect all religious groups, he has not spoken about the recent attacks.

"The prime minister remains silent about this reign of terror. We must assume he dare not alienate evil-doers who support his ideology," Ms Sahgal said in the statement.

She said India's culture of diversity and debate was now "under vicious assault".

"Rationalists who question superstition, anyone who questions any aspect of the ugly and dangerous distortion of Hinduism known as Hindutva - whether in the intellectual or artistic sphere, or whether in terms of food habits and lifestyle - are being marginalised, persecuted, or murdered."

Ms Sahgal told NDTV news channel that under Mr Modi "we are going backwards, regressing, narrowing down to Hindutva... there is rising intolerance and lots of Indians are living in fear".

Poet Ashok Vajpayee has also returned his Sahitya Akademi award, saying that the government has been "promoting violation of rights".

"It's a disturbing trend. It is allowing extra-constitutional agencies to dictate things, whereas it is duty-bound to protect people and writers," he told The Indian Express.